Version: (using KDE 4.3.4) Installed from: Ubuntu Packages Kwin start to use 100% of one of the CPU cores when I open "wine foobar2000.exe" and, right after, I minimize foobar sending it to tray. If, in foobar2000 preferences, I disable the "minimize to tray" feature, Kwin don't goes hi CPU anymore when running the music player and minimize it, because than foobar2000 doesn't go to tray anymore and stay on taskbar. It seems that kwin get lost when try to do something with the task that it just opened but can't see the window listed in the tasklist anymore. That way kwin goes to 100% usage of one of the cpu cores (50% of the total CPU). The high usage just stops after killing kwin and starting it again. While the usage is high, everything seems to work fine anyway, including foobar2000, the system stays responsive.
try to disable "Minimize animation" and "Magic Lamp" and report whether that prevents the high CPU load
Disabled the "Minimize animation", and couldn't reproduce the high CPU load anymore. Enabled "Minimize animation" again, and the high CPU load turns reproducible. As I said before, that happens only when minimize foobar2000 to tray, right after (some seconds) opening it. If I wait some more seconds before minimizing, Kwin will not get itself on high CPU load.
the reason is that obviously foobar/wine triggers a close and a minmize at the same time what used to trouble the minimization FX *** This bug has been marked as a duplicate of bug 184859 ***